1. Technical Field
The present disclosure generally relates to catheters, and, in particular, relates to methods for manufacturing linerless non-prolapsing catheters.
2. Description of Related Art
Catheters are used in medical procedures to gain entry into a body cavity, duct, or vessel to allow drainage, administration of fluids or gases, access by surgical instrument, delivery of medical treatment devices, etc. Catheters may include a single tube or two or more tubes, e.g., coaxial catheters. such as balloon guide catheters. Coaxial catheters have at least an inner tube, an outer tube, and an annular lumen between the inner tube and the outer tube. In a coaxial catheter, the annular lumen may be reduced in cross-sectional area due to prolapse of the outer tube. A reduction in the cross-sectional area of the annular lumen may have an adverse affect on the flow rate of fluids through the annular lumen.
To reduce the risk of prolapse, the outer tube may incorporate a reinforcing structure such as a metal braid or coil to increase the radial strength of the outer tube. In braids, some of the wires are lifted over other wires when they cross. Because such wires are lifted, when constructing the catheter, molten polymer enters the space below the lifted wires thereby interlocking the braid within the polymer.
Sometimes braids may not be suitable for use in a catheter due to its effect on mechanical properties, or because the cross-sectional dimensions of the catheter do not allow for the braid to be included. In these instances, a coil may be used to reinforce the outer tube. In order to improve coil retention, a thin liner is included beneath the coil by winding the coil on the liner. As a result, the coil is disposed between the liner and the polymer after the catheter is constructed.
Due to such factors as dimensional constraints on outer tube diameter/crossing profile, inner tube diameter, and/or annular lumen width, it may be desirable to include a coil but impossible to include a liner. In such cases, there is a significant risk that the coil will delaminate from the tube during the catheter manufacturing process (e.g., during removal of the mandrel or insertion of the inner tube into the outer tube) or afterwards.